Coil and manufacturing method thereof

ABSTRACT

A coil has multiple coil sections connected to each other and each coil section includes a body portion and at least one direct or protrusive connecting portion disposed at one end of the body portion. Coil sections form at least one spiral path around the central axis of the coil, and on the projection of the coil along the central axis. The protrusive connecting portions protrude out of the path location of the direct connecting portions. Two connected coil sections form only one overlapped surface at the coupled parts of the direct or protrusive connecting portions. Regarding to the body portions in the same spiral path, a first end of one body portion is indirectly connected and disposed adjacent to a second end of another body portion. The second end has one surface with a virtual extension reaching the first end.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.14/035,939 filed on Sep. 24, 2013, which claims priority under 35 U.S.C.§119(a) on Patent Application No(s). 101147574 filed in Taiwan, Republicof China on Dec. 14, 2012, and Patent Application No(s). 102115108 filedin Taiwan, Republic of China on Apr. 26, 2013, the entire contents ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION Field of Invention

The present invention relates to a coil and, in particular, to a coilwith high space factor.

Related Art

Inductance devices applied to electromagnets and transformers are mostlycomposed of coil, which is made by winding an enamel wire.

It is desired to provide a coil with low cost and high space factor (orspace coefficient). The space factor is the ratio of the volume occupiedby the wire in the winding to the total volume of the winding. The coilwith higher space factor usually has smaller magnetic loss. Moreover,since the coil is the major component of a motor, the motor can bemanufactured with smaller size, lighter weight and more powerful as thecoil's space factor is increased. Besides, when applying to thehigh-frequency application, the skin effect of the coil current maycause some energy loss. The skin effect is the tendency of analternating electric current (AC) to become distributed within aconductor such that the current density is largest near the surface ofthe conductor, and decreases with greater depths in the conductor. Inthis case, since the flat wire has larger surface area than the circularwire, using the flat wire to manufacture the high-frequency coil caneffectively decrease the energy loss. Moreover, the flat wire also has abetter heat-dissipation capability.

However, since the conventional coil is made by winding the enamel wire,it is hard to increase the space factor thereof. To fabricate a motorwith small size and light weight, the performance of the motor will bedecreased due to the low space factor of the coil. If the coil is madeof a flat wire, it needs a special manufacturing process to form thecoil as the flat surface of the flat wire is perpendicular to thecentral axis of the coil. Accordingly, the manufacturing cost of thecoil by the flat wire is higher.

Therefore, it is an important subject of the present invention toprovide a coil with low cost, high space factor and low energy loss, andmoreover, to provide a coil made of a flat wire.

SUMMARY OF THE INVENTION

In view of the foregoing, an objective of the present invention is toprovide a coil with high space factor and, moreover, to provide a flatcoil with high space factor.

To achieve the above objective, the present invention discloses a coilhaving a plurality of coil sections connected to each other. Each coilsection comprises a body portion and at least one connecting portiondisposed at one end of the body portion and connected with another coilsection. The coil sections form at least one spiral path around thecentral axis of the coil, and two connected coil sections form only oneoverlapped surface at the coupled parts of the connecting portions.Regarding to the body portions in the same spiral path, a first end ofone of the body portions is indirectly connected and disposed adjacentto a second end of another one of the body portions, hereby “indirectlyconnected” means they are connected, especially electrically connected,through at least one connecting portion. Along the spiral path, thesecond end has one surface with a virtual extension reaching the firstend.

In one embodiment, along the spiral path there are one surface of thefirst end and one surface of the second end substantially located on thesame plane, or along the spiral path the second end has one surface witha virtual extension located between two surfaces of the first end, oralong the spiral path the second end has one surface with a virtualextension penetrating through one surface of the first end.

In one embodiment, the coil sections are connected by electroplating orwelding.

In one embodiment, the coil sections are formed by pressing a metalsheet so as to form the connected coil sections, and then the connectingportions are folded to form the coil.

In one embodiment, at least one of the coil sections has different widthand/or different thickness.

To achieve the above objective, the present invention also discloses acoil having a plurality of coil sections connected to each other. Eachcoil section comprises a body portion and at least one direct connectingportion or at least one protrusive connecting portion disposed at oneend of the body portion and connecting with another coil section. Thedirect connecting portions or protrusive connecting portions are foldedor connected by welding, so that the coil sections form at least onespiral path around the central axis of the coil. And on the projectionof the coil along the central axis, the protrusive connecting portionsprotrude out of the path at the location of the direct connectingportions, and two connected coil sections form only one overlappedsurface at the coupled parts of the direct connecting portions or theprotrusive connecting portions.

In one embodiment, regarding to the body portions in the same spiralpath, a first end of one of the body portions is indirectly connectedand disposed adjacent to a second end of another one of the bodyportions, along the spiral path the second end has one surface with avirtual extension reaching the first end, along the spiral path onesurface of the first end and one surface of the second end aresubstantially located on the same plane, or along the spiral path thesecond end has one surface with a virtual extension located between twosurfaces of the first end, or along the spiral path the second end hasone surface with a virtual extension penetrating through one surface ofthe first end.

In one embodiment, the coil sections are formed by pressing a metalsheet so as to form the connected coil sections, and then the directconnecting portions and the protrusive connecting portions are foldedfor once to form the coil.

In one embodiment, the coil sections are divided into two groups, eachgroup of the coil sections is formed by pressing a metal sheet, thecoupled parts of the direct connecting portions and the protrusiveconnecting portions are folded for once, and then the two groups of thecoil sections are intertwined to form the coil.

In one embodiment, the coil sections are connected by electroplating orwelding.

In one embodiment, at least one of the coil sections has different widthand/or different thickness.

To achieve the above objective, the present invention further disclosesa manufacturing method of a coil, comprising the steps of: pressing ametal sheet to form a plurality of coil sections; dispensing a glue onat least one surface of each of the coil sections; providing a pluralityof insulation beads in the glue; and overlapping the coil sections byfolding, or connecting the coil sections by electroplating or welding soas to form a multilayer insulation structure, wherein layers of themultilayer insulation structure are separated by the insulation beads.

In one embodiment, each of the coil sections comprises a body portionand at least one connecting portion disposed at one end of the bodyportion and connecting with another one of the coil sections, theoverlapped coil sections form at least one spiral path around thecentral axis of the coil, and two connected coil sections form only oneoverlapped surface at the coupled parts of the connecting portions.

As mentioned above, the present invention fabricates a plurality of coilsections by pressing or cutting a metal sheet, and then electroplates,welds or folds the coil sections to form a coil. Compared with theconventional manufacturing method of the edge-wound coil, themanufacturing method of the invention is simpler and faster, so that themanufacturing cost can be decreased. Besides, the present invention canimprove the space factor of the coil and can be applied to the flat wirefor decreasing the skin effect, speeding the heat dissipation of thecoil, and making the structure of the coil more solid and more uniformin thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will become more fully understood from the detaileddescription and accompanying drawings, which are given for illustrationonly, and thus are not limitative of the present invention, and wherein:

FIG. 1A is a schematic diagram showing a coil according to a firstembodiment of the invention;

FIG. 1B is a perspective view of a part of a stacked coil of FIG. 1A;

FIG. 1C is another perspective view of a part of a stacked coil of FIG.1A;

FIG. 1D is a perspective view of a variation of a part of a stacked coilof FIG. 1A;

FIG. 1E is another perspective view of a variation of a part of astacked coil of FIG. 1A;

FIG. 1F is a top view of the coil of FIG. 1A;

FIG. 1G is a schematic diagram showing another welded coil according tothe first embodiment of the invention;

FIG. 1H is a perspective view of a part of a stacked coil of FIG. 1G;

FIG. 1I is a schematic diagram showing another coil according to thefirst embodiment of the invention;

FIG. 1J is a perspective view of a part of a stacked coil of FIG. 1I;

FIG. 2A is a schematic diagram showing a coil according to a secondembodiment of the invention;

FIG. 2B is an exploded view of the coil of FIG. 2A;

FIG. 2C is perspective view of a stacked coil of FIG. 2A;

FIG. 2D is a top view of the coil of FIG. 2C;

FIG. 2E is a schematic diagram showing another welded coil according tothe second embodiment of the invention;

FIG. 3A is a schematic diagram showing a coil according to a thirdembodiment of the invention;

FIG. 3B is a schematic diagram showing a wound coil of FIG. 3A;

FIG. 3C is a perspective view of a stacked coil of FIG. 3A;

FIG. 3D is a side view of the coil of FIG. 3C;

FIG. 3E is a top view of the coil of FIG. 3C;

FIG. 4 is a flow chart showing a manufacturing method of a coilaccording to an embodiment of the invention; and

FIG. 5 is a schematic diagram showing a part of the coil sectionsconfigured with an isolation body.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be apparent from the following detaileddescription, which proceeds with reference to the accompanying drawings,wherein the same references relate to the same elements.

FIG. 1A is a schematic diagram showing a coil according to a firstembodiment of the invention, FIG. 1B is a perspective view of a part ofa stacked coil of FIG. 1A, FIG. 1C is another perspective view of a partof a stacked coil of FIG. 1A, FIG. 1D is a perspective view of avariation of a part of a stacked coil of FIG. 1A, FIG. 1E is anotherperspective view of a variation of a part of a stacked coil of FIG. 1A,and FIG. 1F is a top view of the coil of FIG. 1A.

Referring to FIGS. 1A to 1F, a coil 1 includes a plurality of continuouscoil sections 10 a-10 d, which are made by pressing a single metalsheet. The width d of the coil sections 10 a-10 d is, for example butnot limited to, 1 cm. Each of the coil sections 10 a-10 d has a bodyportion 10 and at least one connecting portion 11. The connectingportion(s) 11 is disposed at one end or two ends of the body portion 10.Different body portions 10 and different connecting portions 11 may havedifferent shapes. From the left bottom to right bottom, FIG. 1A showsfour coil sections 10 a-10 d, which are connected with each other. Thecoil section 10 a has a connecting portion 11, the coil section 10 b hastwo connecting portions 11, the coil section 10 c has two connectingportions 11, and the coil section 10 d has two connecting portions 11.The connecting portion 11 of the coil section 10 a is folded along thedotted line onto the connecting portion 11 of the coil section 10 b. Theconnecting portion 11 of the coil section 10 b is folded along thedotted line onto the connecting portion 11 of the coil section 10 c. Theconnecting portion 11 of the coil section 10 c is folded along thedotted line onto the connecting portion 11 of the coil section 10 d.Finally, the coil sections 10 a-10 d form at least one spiral patharound the central axis C of the coil 1. When stacking two groups ofcoil sections 10 a-10 d, the connecting portion 11 of the coil section10 d in a first group is folded along the dotted line onto theconnection portion 11 of the coil section 10 a in the second group.Then, the residual coil sections 10 b-10 d in the second group arestacked thereon by folding the connection portions 11.

To clarify the feature of the connecting portion 11, FIG. 1B only showsthe coil sections 10 a and 10 b. Taking the coil sections 10 a and 10 bas an example, after folding the connecting portion 11 along the dottedline, the top half of the coupled part is the connecting portion 11 ofthe coil section 10 a, while the bottom half of the coupled part is theconnecting portion 11 of the coil section 10 b. Accordingly, the coilsections 10 a and 10 b together form a spiral path around the centralaxis C of the coil 1, and the coupled part of the connecting portions 11forms only one overlapped surface F with a two-layer thickness. To benoted, the overlapped surface F is constructed by folding the connectedcoil sections for once instead of folding them for multiple times.Besides, the overlapped areas of the connecting portions 11 of differentcoil sections are not limited to a rectangle. For example, the coupledparts of the connecting portions 11 may have at least one forkstructure, and two ends of the fork structure may be connected with theconnecting portions of adjacent coil sections, respectively. In thiscase, the connecting portions 11 are also overlapped at an overlappedsurface F. Moreover, the body portion 10 may also have at least one forkstructure, so that the entire coil may contain a plurality of coilsconnected in parallel.

The body portions 10 a 1 and 10 b 1 of the coil sections 10 a and 10 bare located on the same spiral path. The body portion 10 a 1 has a firstend e1 and a second end f2, and the other body portion 10 b 1 has afirst end f1 and a second end e2. The first end e1 and the second end e2are indirectly connected and disposed adjacent to each other. Along thespiral path the second end e2 has one surface with a virtual extensionreaching the first end e1. The coil sections 10 a and 10 b are connectedaround the central axis C to form a basic unit of the spiral path. Asshown in FIG. 1B, the coil sections 10 a and 10 b are configured at asingle wind (or turn) or on the same layer of the spiral path. Whenviewed along a path P of one turn, the body portion 10 a 1 can bereferred to as a preceding body portion of the turn, and the bodyportion 10 b 1 can be referred to as the succeeding body portion of theturn. Therefore, the first end f1 of the body portion 10 b 1 isconnected to the connecting portion 11 disposed at the second end f2 ofthe body portion 10 a 1 (i.e. the preceding body portion), and thebottom surface at the second end f2 of the body portion 10 a 1 isoverlapped with the top surface at the first end f1 of the body portion10 b 1 (i.e. the succeeding body portion). Referring to FIG. 1C, thecoil sections 10 a and 10 b are connected to form a single wind (or abasic unit of the spiral path), and the coil sections 10 c and 10 d areconnected to form another single wind (or another basic unit of thespiral path). In this embodiment, a basic unit of the spiral path iscomposed of two coil sections. Of course, a basic unit of the spiralpath can be composed of two or more coil sections, which will bedescribed with reference to the following drawings.

Please refer to FIGS. 1B, 1D and 1E. In this embodiment, the coilsections 10 a and 10 b are flat, and the surfaces of the coil sections10 a include the top surfaces and the bottom surfaces thereof. As shownin the figures, the second end e2 has one surface (top surface) with avirtual extension (defined by the dotted lines) reaching the first ende1 along the spiral path. One surface of the first end e1 and onesurface of the second end e2 are substantially located at the sameplane. Referring to FIG. 1B, the top surface of the first end e1 and thetop surface of the second end e2 are located at the same plane. As shownin FIG. 1D, along the spiral path one surface (top surface) of thesecond end e2 has a virtual extension located between two surfaces ofthe first end e1. As shown in FIG. 1E, along the spiral path one surface(bottom surface) of the second end e2 has a virtual extensionpenetrating through one surface (top surface) of the first end e1. To benoted, the virtual extension is not a real existing surface.

FIG. 1G is a schematic diagram showing another welded coil according tothe first embodiment of the invention, and FIG. 1H is a perspective viewof a part of a stacked coil of FIG. 1G.

Referring to FIGS. 1G and 1H, the coil 2 includes a plurality ofseparated coil sections, such as four separated coil sections 20 a-20 d,which are made by pressing a single metal sheet. The width d of the coilsections 20 a-20 d is, for example but not limited to, 1 cm. Each of thecoil sections 20 a-20 d has a body portion 20 and at least oneconnecting portion 21. The connecting portion(s) 21 is disposed at oneend or two ends of the body portion 20. Different from the previousaspect, the connecting portions 21 of the coil sections 20 a-20 d of thecoil 2 are all disposed inside the body portion 20 and each have awelding point (see the dot in the figures) for connecting to theconnecting portion 21 of the adjacent coil section by welding orelectroplating. In this aspect, the connecting portion 21 of the coilsection 20 a is welded on top of the connecting portion 21 of the coilsection 20 b, the connecting portion 21 of the coil section 20 b iswelded on top of the connecting portion 21 of the coil section 20 c, andthe connecting portion 21 of the coil section 20 c is welded on top ofthe connecting portion 21 of the coil section 20 d. After connecting andstacking the coil sections 20 a-20 d by welding or electroplating, apart of the stacked coil sections as shown in FIG. 1H can bemanufactured.

FIG. 1I is a schematic diagram showing another coil according to thefirst embodiment of the invention, and FIG. 1J is a perspective view ofa part of a stacked coil of FIG. 1I.

Referring to FIGS. 1I and 1J, the coil 3 includes a plurality ofcontinuous coil sections 30 a, 30 b and 30 c, which are made by pressinga single metal sheet. Each of the coil sections 30 a-30 c has an arcshape and includes a body portion 30 and at least one connecting portion31. The connecting portion(s) 31 is disposed at one end or two ends ofthe body portion 30. Besides, as shown in FIG. 1J, one wind (a basicunit of the spiral path) of the coil 3 is composed of three coilsections 30 a, 30 b and 30 c, which is different from the previousaspects. The indirectly connected ends of the coil sections 30 a and 30b are located at different planes, and the indirectly connected ends ofthe coil sections 30 b and 30 c are also located at different planes.The second end e2 of the body portion 30 of the coil section 30 c andthe first end e1 of the body portion 30 of the coil section 30 a aredisposed adjacent to each other and indirectly connected. Along thespiral path the top surface of the second end e2 has a virtual extensionreaching the first end e1, and the top surfaces of the first end e1 andthe second end e2 are substantially located at the same plane (see thedotted circle). Accordingly, the connected two coil sections are notnecessarily to be the two coil sections that have their endssubstantially located at the same plane. That is, the connected coilsections 30 a and 30 b or the connected coil sections 30 b and 30 c forma single overlapped surface at the coupled parts of the connectingportions 31, and the indirectly connected ends (e1 and e2) of the bodyportions 30 of the two adjacent coil sections 30 a and 30 c aresubstantially located at the same plane. In practice, along the spiralpath one surface of the first end e1 and one surface of the second ende2 can be substantially located on the same plane, or along the spiralpath the second end e2 has one surface with a virtual extension locatedbetween two surfaces of the first end e1, or along the spiral path thesecond end e2 has one surface with a virtual extension penetratingthrough one surface of the first end e1.

As mentioned above, the coil is manufactured by pressing a metal sheetand then folding or welding/electroplating the coil sections. Thismanufacturing method is simple and suit for mass production, and themanufacturing cost of the coil is much lower than the conventionalwinding coil. Moreover, the coil of the embodiment is flat, so that itcan provide higher space factor, lower skin effect and better heatdissipation.

To be noted, the numbers of the coil sections in the coils 1, 2 and 3can be adjusted according to the requirements of the products.Similarly, the width d and thickness of the coil sections can bedifferent according to the requirements of the products. For reducingthe skin effect, the area or perimeter of the cross-section of each coilsection is substantially remained the same so as to prevent theundesired loss.

FIG. 2A is a schematic diagram showing a coil according to a secondembodiment of the invention, and FIG. 2B is an exploded view of the coilof FIG. 2A.

Referring to FIGS. 2A and 2B, the coil 4 includes a plurality ofcontinuous coil sections, such as four continuous coil sections 40 a-40d, which are made by pressing a single metal sheet. The shapes of thecoil sections 40 a-40 d are totally different, and the width d of thecoil sections 20 a-20 d is, for example but not limited to, 1 cm. Eachof the coil sections 40 a-40 d has a body portion 40 and a directconnecting portion 41 or a protrusive connecting portion 42. The directconnecting portion 41 or the protrusive connecting portion 42 isdisposed at one end or two ends of the body portion 40. As shown in FIG.2B, the coil section 40 a has a direct connecting portion 41, the coilsection 40 b has a direct connecting portion 41 and a protrusiveconnecting portion 42, the coil section 40 c has two protrusiveconnecting portions 42, and the coil section 40 d has a protrusiveconnecting portion 42. The protrusive connecting portions 42 protrudeout at the path location of the direct connecting portions 41, and twoconnected coil sections form only one overlapped surface at the coupledparts of the direct connecting portions 41 or the protrusive connectingportions 42.

In this embodiment, the body portions 40 of the coil sections 40 a-40 dare substantially U-shaped. As shown in FIG. 2C, the coil sections 40 aand 40 b form a wind (a basic unit of the spiral path). Regarding to thebody portions of the coil sections 40 a and 40 b, the first end e1 ofthe body portion of the coil section 40 b and the second end e2 of thebody portion of the coil section 40 a are disposed adjacent to eachother and are indirectly connected. Besides, along the spiral path thetop surface of the second end e2 has a virtual extension reaching thefirst end e1. As shown in the figures, the virtual extension of the topsurface of the second end e2 and the first end e1 are substantiallylocated at the same plane. In practice, except for the aboveconfiguration, along the spiral path one surface of the second end e2may have a virtual extension located between two surfaces of the firstend e1, or along the spiral path one surface of the second end e2 mayhave a virtual extension penetrating through one surface of the firstend e1. To be noted, the second end e2 is directly disposed on thedirect connecting portion 41 and is also a part of the body portion 40 a1. The first end e1 is disposed on the body portion 40 b 1, and theprotrusive connecting portion 42 is connected with the first end e1 ofthe body portion 40 b 1.

FIG. 2C is a perspective view of a stacked coil of FIG. 2A, and FIG. 2Dis a top view of the coil of FIG. 2C.

Referring to FIGS. 2A to 2D, the direct connecting portion 41 of thecoil section 40 a is folded onto the direct connecting portion 41 of thecoil section 40 b. The protrusive connecting portion 42 of the coilsection 40 b is folded onto one of the protrusive connecting portions 42of the coil section 40 c. The other protrusive connecting portion 42 ofthe coil section 40 c is folded onto the protrusive connecting portion42 of the coil section 40 d. Finally, the coil sections 40 a-40 d form aspiral path around the central axis C of the coil 4. In addition, a partof the body portion 40 of the coil section 40 b (the middle part) isformed with an oblique surface, so that the top surface of the bodyportion 40 of the coil section 40 b is gradually rising from the bottomsurface of the body portion 40 of the coil section 40 a to the topsurface of the body portion 40 of the coil section 40 a. That is, thetop surface of the body portion 40 of the coil section 40 b obliquelyextends across one layer's height. Similarly, the top surface of thebody portion 40 of the coil section 40 d is gradually rising from belowthe bottom surface of the body portion 40 of the coil section 40 c tothe top surface of the body portion 40 of the coil section 40 c. Thecoil 4 can be manufactured by stacking the coil sections 40 a-40 d asshown in FIGS. 2C and 2D, wherein the coil sections 40 a-40 d aretightly stacked.

In the above aspect, only the coil sections 40 b and 40 d have theoblique surfaces. In practice, the other coil sections 40 a and 40 c mayalso have the oblique surfaces. The four coil sections 40 a-40 d arefolded to form a structure containing the protrusive connecting portions42 and a rectangular main coil zone Z (see dotted block in FIG. 2Dsurrounding the central axis C), which is composed of the main bodies 40and the direct connecting portions 41. The protrusive connectingportions 42 protrude out at the path location of the direct connectingportions 41. That is, the protrusive connecting portions 42 protrude outof the main coil zone Z. Two connected coil sections form only oneoverlapped surface F (see the dotted-line area in FIG. 2D) at thecoupled parts of the direct connecting portions 41 or the protrusiveconnecting portions 42. To be noted, the overlapped surface F isconstructed by folding the adjacent coil sections for once instead offolding them for multiple times, so the folded area has a minimum heightof two layers. Besides, the overlapped areas of the direct connectingportions 41 or the protrusive connecting portions 42 are not limited toa rectangle. The coupled parts of the direct connecting portions 41 orthe protrusive connecting portions 42 may have at least one dividedstructure. For example, the direct connecting portions 41 have a dividedstructure. Two ends of the divided structure may be connected with thedivided body portion 40 and the divided protrusive connecting portion42. In this aspect, the direct connecting portions 41 or the protrusiveconnecting portions 42 are still connected at an overlapped surface F,so that the entire coil 4 may contain a plurality of coils connected inparallel.

FIG. 2E is a schematic diagram showing another welded coil according tothe second embodiment of the invention. Referring to FIG. 2E, the coil 5includes separated two groups of coil sections 50 a-50 d (totally 8 coilsections). The direct connecting portion 51 of the coil section 50 a iswelded onto the direct connecting portion 51 of the coil section 50 b,the protrusive connecting portion 52 of the coil section 50 b is weldedonto one of the protrusive connecting portions 52 of the coil section 50c, and the other protrusive connecting portion 52 of the coil section 50c is welded onto the protrusive connecting portion 52 of the coilsection 50 d. The welding method is disclosed in the first embodiment,so the detailed description thereof will be omitted here. The weldingaspect is repeated to connect the 8 coil sections 50 a-50 d. Inpractice, the number of the coil sections may be various depending onthe requirements of the products, and this invention is not limited.Besides, the coil sections can also be connected by folding orelectroplating.

FIG. 3A is a schematic diagram showing a coil according to a thirdembodiment of the invention, FIG. 3B is a schematic diagram showing awound coil of FIG. 3A, FIG. 3C is a perspective view of a stacked coilof FIG. 3A, FIG. 3D is a side view of the coil of FIG. 3C, and FIG. 3Eis a top view of the coil of FIG. 3C.

As shown in FIG. 3A, the coil 6 includes a coil string 6 a and a coilstring 6 b, which are composed of a plurality of continuous coilsections 60 a and 60 b by pressing a single metal sheet. The coilsections 60 a and 60 b are alternately configured, and each of the coilstrings 6 a and 6 b contains three coil section 60 a and two coilsections 60 b. The width d of the coil sections 60 a and 60 b is, forexample but not limited to, 1 cm. Each of the coil sections 60 a and 60b includes a body portion 60 and a direct connecting portion 61 or aprotrusive connecting portion 62. The direct connecting portion 61 orthe protrusive connecting portion 62 is disposed at one end or two endsof the body portion 60. From the left to the right, the coil section 60a includes a direct connecting portion 61 and a protrusive connectingportion 62, and the coil section 60 b includes a direct connectingportion 61 and a protrusive connecting portion 62.

Referring to FIGS. 3A to 3E, in the coil string 6 a, the directconnecting portion 61 of the coil section 60 a is directly connectedwith the direct connecting portion 61 of the coil section 60 b (with onefolding line), and the protrusive connecting portion 62 of the coilsection 60 b is directly connected with the protrusive connectingportion 62 of the next coil section 60 a (with one folding line).Accordingly, the folding procedure of the coil string 6 a can befinished by folding the direct connecting portions 61 or the protrusiveconnecting portions 62 of the adjacent coil sections 60 a (along thedotted folding line). After folding the coil string 6 b by the sameprocedure, the coil string 6 a and the coil string 6 b can respectivelyform a half wind and alternately twisted in a dual spiral structure (seeFIG. 3B). As a result, the two coil sections 60 a and 60 b can form atwisted spiral path around the central axis C stacked as shown in FIG.3C. After folding the multiple coil sections 60 a and 60 b, the coil 6contains the protrusive connecting portions 62 and the rectangular maincoil zone Z (see dotted block of FIG. 3E surrounding the central axis C)composed of the body portions 60 and the direct connecting portion 61.The protrusive connecting portions 62 protrude out at the path locationof the direct connecting portions 61. That is, the protrusive connectingportions 62 protrude out of the main coil zone Z. Two connected coilsections form only one overlapped surface F (see the dotted-line area inFIG. 3E) at the coupled parts of the direct connecting portions 61 orthe protrusive connecting portions 62. FIG. 3C shows two twisted groupsof coils, and these two groups of coils are connected in parallel or inserial, or separated according to the user requirements.

In this embodiment, the body portions 60 of the coil sections 60 a and60 b are substantially U-shaped. As shown in FIG. 3C, the coil section60 a of the coil string 6 a and the coil section 60 b of the coil string6 b form a wind (a basic unit of the spiral path). Regarding to the bodyportions of the coil sections 60 a of the coil string 6 a and 6 b, alongthe spiral path the top surface of the second end e2 has a virtualextension reaching the first end e1 of the body portions of the coilsections 60 a of the coil strings 6 a and 6 b. As shown in the figures,the virtual extension of the top surface of the second end e2 and thefirst end e1 are substantially located at the same plane (see FIGS. 3Cand 3D). In practice, except for the above configuration, one surface ofthe second end e2 may have a virtual extension located between twosurfaces of the first end e1 along the spiral path, or one surface ofthe second end e2 may have a virtual extension penetrating through onesurface of the first end e1 along the spiral path. To be noted, thesecond end e2 is directly disposed on the direct connecting portion 61and is also a part of the body portion 60 a 1. The first end e1 isdisposed on the protrusive connecting portion 62 of the body portion 40b 1, and the protrusive connecting portion 62 is connected with thefirst end e1 of the body portion 60 b 1.

FIG. 4 is a flow chart showing a manufacturing method of a coilaccording to an embodiment of the invention, and FIG. 5 is a schematicdiagram showing a part of the coil sections configured with an isolationbody. The coils of the first to third embodiments can be manufactured bythe manufacturing method of a coil as shown in FIG. 4. To clarify therelations between the flow chart and the other drawings, the followingexample illustrates the manufacturing method of a coil applied to foldthe coil sections 10 a and 10 b of the first embodiment.

The manufacturing method of a coil of the invention includes thefollowing steps S01 to S04. The step S01 is to press a metal sheet toform a plurality of coil sections 10 a and 10 b. The step S02 is todispense a glue S1 on an external surface or any of the coil sections 10a and 10 b. In the step S03, a plurality of insulation beads P areprovide in the glue S1. The step S04 is to overlap and connect the coilsections 10 a and 10 b by folding, electroplating or welding so as toform a multilayer insulation structure. Herein, the coil section 10 b isstacked on the coil section 10 a, and an insulation body S composed ofthe glue S1 and the insulation beads P is interposed between the coilsections 10 a and 10 b for separating the coil sections 10 a and 10 b.Besides, the steps S02 and S03 can be combined into a single process.For example, the insulation beads P and the glue S1 are mixed inadvance, and then the mixture is spread on the external surface or anysurface of the coil sections 10 a and 10 b.

The coil can be manufactured by folding and stacking more coil sectionsdepending on the product requirement. If necessary, a baking step may beprovided to solidify the insulation beads P and the glue S1 so as toform the insulation body S. To be noted, the scales of the insulationbeads P and the glue S1 are enlarged in FIG. 5 for illustration purpose.

Accordingly, the multiple layers of the coil sections in themanufactured coil can be gapless or with a smallest gap, so that thespace factor can be significantly increased. Besides, the shape of thecoil sections is not limited and can be, for example, circular,rectangular, triangular, or polygonal. In this invention, the coilsections are formed by pressing or cutting a metal sheet, and then thecoil sections are folded or welded to manufacture the desired coil. Asmentioned above, the manufacturing procedure of the coil of theinvention is simpler and faster than that of the conventional flatwinding coil. The present invention is to fold and stack the coilsections for fabricating the desired coil, so that it is possible tomanufacturing a multilayer flat coil with a fast and low cost approach.

Although the invention has been described with reference to specificembodiments, this description is not meant to be construed in a limitingsense. Various modifications of the disclosed embodiments, as well asalternative embodiments, will be apparent to persons skilled in the art.It is, therefore, contemplated that the appended claims will cover allmodifications that fall within the true scope of the invention.

What is claimed is:
 1. A coil having a plurality of turns distributedalong a central axis of the coil, each turn having at least two coilsections, each of the at least two coil sections comprising: a bodyportion having a first end and a second end, and a top surface facingalong one direction of the central axis of the coil, and a bottomsurface facing the opposite direction to the top surface; wherein of theat least two coil sections, one coil section is connected and partiallyoverlapped with the other coil section by folding; wherein each of theat least two coil sections except a last coil section at a last turnfurther comprises at least one direct connecting portion or at least oneprotrusive connecting portion disposed at the second end of the bodyportion; and wherein in one turn of the coil, except a first end of aleading body portion at the beginning of the turn, the first end of theother body portions in a same turn is connected to the direct connectingportion or the protrusive connecting portion disposed at a second end ofa preceding body portion, and a second end of a ending body portion atthe last of the same turn is aligned toward and kept distance from thefirst end of the leading body portion, and a cross section of the secondend of the ending body portion is overlapped with a cross section of thefirst end of the leading body portion when viewed along the path of theturn.
 2. The coil according to claim 1, wherein the at least two coilsections are formed by pressing a metal sheet so as to form theconnected coil sections, and then the direct connecting portions and theprotrusive connecting portions are folded to form the coil.
 3. The coilaccording to claim 1, wherein the at least two coil sections are dividedinto two groups, and the two groups of the coil sections are intertwinedto form the coil.
 4. The coil according to claim 1, wherein the at leasttwo coil sections are connected by electroplating or welding.
 5. Thecoil according to claim 1, wherein at least one of the coil sections inthe plurality of turns has different width or different thickness.